1. Field of the Invention
The present invention generally relates to a reversing switch and more particularly a diaphragm operated electrical polarity reversing switch which has general utility but in the application the reversing switch is disclosed for use in combination with a vehicle mounted spray device including a discharge nozzle which may be used for applying chemicals, liquid fertilizers and other liquids such as when applying such materials alongside of roadways to effectively apply liquid throughout the width of the road right-of-way in which spray nozzles are mounted adjustably on a pivotal arm-type support assembly at the right front of a vehicle and a control arrangement is oriented in the cab of the vehicle to enable the vehicle operator to control the spray apparatus. A diaphragm is communicated with a pressurized supply line with the diaphragm being responsive to pressure in the supply line together with a control valve to direct flow to one of a plurality of different sized nozzles in order to maintain a constant pressure of liquid at each nozzle with any temporary variation in the pressure caused by switching from one nozzle to another being promptly corrected thus providing a constant flow rate and constant width of discharge of liquid from the nozzle.
2. Description of the Prior Art
Various efforts have been made to discharge liquids from nozzles in a manner to maintain a predetermined rate of discharge on a given area when the nozzle is moved over the area at a given speed. The following U.S. Pat. Nos. 2,837,611, 2,996,588, 3,260,816, 4,315,602, 4,525,698, 4,875,235, 4,892,985, and 5,076,497 relate to this field of endeavor.
The above patents disclose various structures relating to spray nozzles and diaphragm operated switches as well as a switch that will reverse polarity of a DC motor to provide selective rotational output from the motor. However, none of the patents disclose a reversing polarity switch utilizing a neutral position and to effectively and quickly retain a constant discharge pressure supplied to spray nozzles having different discharge rates.
All spray nozzles used for applying chemicals, liquid fertilizers and other liquids contain an orifice of a specific size to regulate the flow of liquid through the nozzle. In order to use spray nozzles, it is first necessary to determine the amount of spray per acre or per yard or some other unit of surface measurement. For the purpose of this report, per acre will be used as the unit of surface measurement.
Once the amount of liquid desired per acre at a given speed and pressure has been determined, the nozzle size then can be selected. All spray nozzles currently being manufactured are supplied with charts which give their flow rate in gallons per minute and in gallons per acre at several operating pressures as well as at a variety of operating speeds.
Spray nozzles used on boom sprayers normally have band widths from a few inches up to about five feet. A boom sprayer with a twenty foot boom on either side of the sprayer, for a total boom width of forty feet, can have as few as eight and up to thirty or more spray nozzles attached. Some special application sprayers have been lengths of up to eight feet.
Boomless spray nozzles, as the name implied, operate without the need for booms. Some manufacturers group together a cluster of straight stream nozzles with a variety of orifice sizes. The smallest nozzle in angled down to spray the area nearest to the sprayer. The next nozzle is angled to spray a few inches further out and so on until all of the nozzles in the cluster are used to spray a given pattern width.
Other boomless nozzles such as that disclosed in U.S. Pat. No. 5,076,497 are designed to spray in a fan-type pattern and require only one nozzle to spray a given distance. If more than one pattern width is required, such as in right-of-way spraying, a separate nozzle will be needed for each pattern width.
Boom-type arrangements, cluster nozzles and nozzles shown in U.S. Pat. No. 5,076,497 require among other things three basic items in order to operate properly. First, all require a pump with a power source to supply the nozzles with a pressurized liquid. These pumps and their power sources vary widely in size and are selected to match the needs of a particular sprayer.
Second, they must have one or more valves, depending on the number of nozzles or clusters, in order to turn the sprayer on and off. Several different types of valves used for this purpose are available. Most of these valves operate either manually or electrically.
Third, all must have some type of device to maintain consistant pressure on the nozzle or nozzles while spraying. The most commonly used device for this purpose is a manually-set bypass-type pressure regulator. This is a spring-loaded device with a threaded screw handle. When the handle is turned clockwise, it tightens the spring which is resting against a valve located in a seat within the regulator. The increase in valve spring pressure requires a corresponding increase in liquid pressure to overcome the spring pressure and open the bypass valve thus increasing the pressure on the nozzle or nozzles.
Likewise, turning the handle counterclockwise will produce less pressure on the nozzle or nozzles. A single regulator of this type will not maintain a constant pressure on two or more nozzles in a system requiring different flow rates.
Two other devices used to control pressure in sprayers are the ball valve and the butterfly valve. When used on mobile spraying equipment, these valves are operated by small twelve volt DC motors which are powered by the battery of the spraying vehicle. The motor is connected to the valve through a speed reducing gear mechanism. This type of valve can require from a few to several seconds to travel from fully open to fully closed. When used as a pressure regulator on spraying vehicles, these valves can be placed in line upstream of the nozzles thus controlling the pressure on the nozzles.
In almost all spraying applications, at one time or another, it becomes necessary to use only a portion of the equipment's total band width. For example, a sprayer with a total band width of forty feet may need to be temporarily reduced to twenty feet or to ten feet for narrow areas such as around field edges in agriculture. In right-of-way spraying, the need to change band widths occurs much more frequently.
In order to accommodate these changing needs with manually set bypass-type regulators, each boomless nozzle, nozzle cluster or boom section must have its own bypass regulator. Each of these bypass regulators, as the name implies, must have a bypass or return line from the regulator to the liquid supply tank. In some cases, synchronizing several of these regulators to maintain a constant pressure in the various modes of the sprayer operation becomes very difficult.
When using electrically operated ball or butterfly valves as pressure regulators, the job of maintaining constant nozzle pressure on all of the nozzles becomes somewhat simpler. Since the motors in ball and butterfly valves operate on DC current, they will operate either clockwise or counterclockwise. They can be instantly reversed by reversing the electrical polarity to the motor with a double-pole double-throw normally-open type manually operated switch.
These valve are usually controlled from a remote control panel conveniently located near the equipment operator. A remote control panel of this type would normally contain a master switch for turning the unit on and off. It would contain a pressure gauge for monitoring pressure and may contain one or more switches for selecting different nozzles or boom sections for the purpose of spraying various band widths.
In almost all spraying operations, it is usually desirable for the spraying vehicle to maintain a constant speed as well as to maintain a constant liquid pressure on all of the nozzles regardless of flow rates or band widths. In order to maintain constant pressure on the system when using motorized ball or butterfly valves, the control panel must contain an electrical polarity reversing switch.
For example, assume that a nozzle or boom section spraying a ten foot band width will apply the desired amount of liquid per acre at ten miles per hour operating at forty pounds of pressure. When the sprayer is turned on, the operator must observe the pressure gauge and either open or close the motorized valve manually with the polarity reversing switch as necessary to obtain the desired forty pounds of pressure on the nozzle or boom section in use. Each time the operator changes band widths by switching from one nozzle to another, the pressure must be readjusted also using the motorized valve. In right-of-way spraying, this switching and readjusting can occur as often as several time in a matter of a few minutes.
Switching from one nozzle to another by the operator can usually be accomplished fairly quickly. However, resetting the nozzle pressure each time after switching band widths can require several seconds. Since the driver must direct his attention to the pressure gauge while manipulating the pressure resetting switch, and away from driving the vehicle, a hazardous situation could occur.
This scenario prompted the beginning of our efforts to develop a simpler and safer method of maintaining constant pressure automatically on sprayers equipped with multiple band width requirements. After some time, we were able to develop such a device which we refer to as a smart switch. The generic description for this switch is a pressure-sensitive electrical polarity reversing switch with neutral capability.
When using this switch to maintain constant pressure on multiple band width spraying equipment or other liquid handling equipment requiring constant pressure on multiple flow rates, the switch must be used in conjunction with an electric motorized ball or butterfly valve. What this switch does in essence is to supply the motorized valve with current in the proper polarity to open or to close the valve in the proper amount to allow for the proper flow rate through the valve sufficient to produce the desired preset nozzle pressure.
Each time a different size nozzle, boom section or cluster of nozzles is selected during the spraying operation, the smart switch senses a pressure change in the system caused by the change in flow rate. When the smart switch senses this change, it activates the motorized valve which makes the necessary flow correction to maintain the proper pressure in about two seconds.